Storage tanks are widely used for storing a variety of liquids. Some of these liquids are hazardous and can be corrosive and/or flammable. In particular, underground storage tanks are used extensively for the storage of liquid gasoline at retail gasoline stations. Typical underground storage tanks are constructed with structural accessories such as a manway, its lid, and access lines for filling, dispensing, and venting. The accessories described are examples of structures through which liquids and vapors flow and all of which are normally located at the top of the tank.
The service life of a storage tank system will vary, but eventually the tank and its access lines will leak. Leaks from the tank system often happen within a few years after the new tank and lines are installed, due to improper installation or flaws in the manufacturing of the tanks and lines. Leakage problems are particulary troublesome in that gasoline storage tanks are usually buried underground. Any leaks which develop are normally very slow initially and are very difficult to detect. Leaks from subterranean tanks or their accessories can result in a significant danger to the environment and health of nearby residents. Federal as well as local regulations govern the design and maintenance of such storage tanks.
Heightened public awareness of the danger posed by underground storage tanks has led to additional governmental regulations. Recent proposed regulations will require most storage tanks to have secondary containment means and possibly a fail safe leak detection design feature to guard against accidental soil and water contamination. Secondary containment is accomplished by a jacket completely encasing the tank and structural accessories. The tank and related accessories are referred to as the primary containment system. Any jacket or wall encasing the primary system is often referred to as a secondary containment system.
There now has been discovered a secondary containment system encasing the fill line and, optionally, other structural accessories of a liquid underground storage tank. The storage tank itself can have a secondary containment feature. The present invention solves the problems inherent with existing tank systems with provisions for leak detection means.